Moderator touching barrel during firing

[SSN100]

I have a .308 with a very thin 22” barrel and I use an over barrel mod - S&L venom which extends quite far back. While there is a good gap between barrel and mod a distinct mark has formed creating a ring all the way around the barrel at the rear of the mod. This isn’t from putting the moderator on, so I can only assume it is to do with harmonics and the moderator and barrel are making contact during the firing cycle. Is this possible and if it is, it presumably could effect accuracy by interfering g with the harmonics. Would I be better switching to an end can?

 

[Foxyboy43]

Hmmm.
In my experience Reflex moderators (like yours) usually have an insert which is a snug fit to the barrel and is usually made of some fairly tough man-made material which is supposed to prevent said ring appearing and if you listen to some “trueing” the mod to the barrel, though others say this is unnecessary if the barrel has been properly threaded. The ring is often caused simply by the screwing action of tightening the mod. In all my years of using these moderators they have always left varying degrees of a ring on the barrel.

 

[VSS]

Could you put a bit of tape around the barrel at that point, to prevent marking?

 

[Greenmist]

As above, fitting and removing the mod will cause slight wear, bushing supposedly should have 0.002 clearance. Never had one effect accuracy, if you're concerned, try firing with and without the bushing to see if it makes any difference

 

[SSN100]

I've looked at this again and concluded it must be from me putting it on and off. There is no bushing on this model so the small amount of contact before the threads properly engage must be causing the marking. Icobviously need to be a bit more careful and I will add something to protect the barrel.

 

[bluesako]

i wouldnt worry all my barrels have a mark on them crack on bs

 

[Stevie/P]

Small length of shrink wrap will prevent rubbing

 

[SSN100]

i wouldnt worry all my barrels have a mark on them crack on bs

Not overly worried, it is a tool, and might end up shortening anyway, but might as well avoid removing the protective coating if I can.

 

[flatliner]

My cz527 came with a T8 moderator fitted a bushing, which like your's had marked the barrel. I have since fitted a DPT moderator and I didn't bother with the supplied bush, and have found it has made no difference whatsoever to the rifle's accuracy.

 

[SSN100]

Small length of shrink wrap will prevent rubbing

I just cut a bit of bicycle inner tube.